Process for crimping filaments

ABSTRACT

A PROCESS FOR MAKING CRIMPED POLYESTER FILAMENTS HAVING SPECIAL PROPERTIES COMPRISES MELT-SPINNING THE FILAMENTS, LIQUID-QUENCHING THE HOT FILAMENTS ASYMMETRICALLY BY CONTACTING ONE SIDE OF THE FILAMENTS WITH A CONTINUOUSLY RENEWED THIN FILM OF LIQUID ON A SOLID TAPERED BODY LOCATED BELOW THE SPINNERET, DRAWING THE FILAMENTS, RELEASING THE TENSION TO DEVELOP CRIMP AND THEN HEAT-SETTING THE CRIMPED FILAMENTS.

Dec. 21, 1971 P. E. KNAPP PROCESS FOR CRIMPING FILAMENTS Origina l Filed Feb. 5, 1965 United States Patent US. Cl. 264-168 12 Claims ABSTRACT OF THE DISCLOSURE A process for making crimped polyester filaments having special properties comprises melt-spinning the filaments, liquid-quenching the hot filaments asymmetrically by contacting one side of the filaments with a continuously renewed thin film of liquid on a solid tapered body located below the spinneret, drawing the filaments, releasing the tension to develop crimp and then heat-setting the crimped filaments.

This is continuation of Ser. No. 430.686, filed Feb. 5, 1965, and now abandoned.

This invention relates to crimped fibres of synthetic linear polyesters particularly those based on terephthalic acid.

These polyester fibres have particular advantages as filling material for items such as pillows, quilts and cushions and also in textile fabrics.

In our British Pat. 809,273 a process is described for the manufacture of potentially crimpable synthetic linear polymer filaments capable of showing their full crimp after a treatment including drawing and shrinking, which comprises quenching a bundle of hot filaments unsymmetrically, in a melt spinning process, by causing the filaments during their travel from the spinnneret to a winding device to come into contact with a continuously renewed thin film of a liquid on the surface of a solid body and which is at a temperature considerably below that of the filaments, the bundle of filaments contacting the film of cooler liquid in such a manner that one side only of each filament contacts the film of liquid. The as-spun filaments are then drawn. It is stated that the process is particularly suitable for the production of crimped filaments having a copious crimp and that the crimped filaments can also be cut up into staple length. if desired. The resulting fibres may then be used in the usual way for textile manufacture or blended with other staple fibres.

According to the present invention we provide crimped fibres made by meltspinning, liquid quenching and drawing a synthetic linear polyester in which said fibres have a tenacity of 2-6 g./den. an extension to break of 15 %-60% an initial modulus of 25-40 gm./ den a crimp index of 15- 70%, a crimp level of 2-13 crimps per straight inch, a mean rate of change of instantaneous modulus, between 5% and extension, of 90-160 gm./ denier and a denier of 1-6, an asymmetry of refractive index of not less than 1.l0 measured across the Width of the fibre. Suitable fibres preferably have a shrinkage when immersed in boiling water for 1 minute of less than 1%.

These fibres are particularly suitable in a staple length of 1" to 10". When made into a batt they can provide a specific volume of 35-40 cm. gm. when under a pressure of 10 gm. wt./cm. and after repeated loadings to this pressure, whereas fibres of a similar denier but having a two dimensional crimp. cannot exceed a specific volume of 30 cm. gm. under these conditions. Moreover the helically crimped fibres have a greater resilience and recover more completely from compression than do two dimensionally "ice crimped fibres. They are therefore especially suited for filling upholstery, pillows, :bed quilts, light weight quilting such as house coats, sleeping bags, and the like. When made into fabrics by the conventional textile processing routes, the fibres lead to fabrics which have improved crease recovery, bulk and covering power.

Further, in accordance with our present invention we provide a process for making our helically crimped fibres comprising meltspinning the polyester and liquid quenching the filaments on a Water covered surface below the spinneret at a distance between 4 and 14 inches below the spinneret followed by drawing. At less than 4 inches running difiiculties are experienced. whilst at more than 14 inches a negligible amount of crimp is produced and which is unsuitable for producing our specified fibres. The preferred surface is provided by a hollow vitreous bonded ceramic aggregate, which is sufficiently porous to permit the slow passage of water or of an aqueous solution. The length of the quenching surface in the direction of travel of the melt-spun filament is preferably /2 to 1 /2 inches. provided that an adequate tension is induced in the threadline. We have found that a tension of 0.06 gm./ denier is suitable and that the tension should not be less than 0.02 gm./denier in order to produce the specified crimp.

The amount of crimp developed in the drawn fibre depends on the size of the spinneret hole. The perferred size is a 0.015 inch diameter circular hole which gives satisfactory running and adejuate crimp. However. it is a comprimise between good running but less crimp with smaller diameter holes of about 0.009 inch. and more crimp but poorer running with spinneret holes of larger diameter of about 0.03 inch. Under the foregoing conditions wind-up speeds up to 4500 ft./min. can be successfully employed. The preferred speeds are about 3000 ft./rnin. but compensation for reduction of hole size or increase of spinneretquench distance may be made by increasing the wind up speed. because the crimp level and the crimp index both increase with the wind up speed.

We have found that so long as there is sufficient water to hold the filaments in place on the ceramic quenching surface, the crimp level and crimp index are independent of the water flow. Using a cotton fabric as a quenching surface however. the crimp increases as the water flow diminishes. The flow rates employed have fallen within the range 0.5 to 1.5 cm. /min. per square centrimetre of useful quenching surface. Referring these flow rates to the filament number. gives a range of 0.5 to 0.9 cm. /min./filament.

For a given wind up speed, hole size, and quench surface position, the crimp increases with the spun denier per filament. Suitable spinning temperatures for polyethylene terephthalate vary with the intrinsic viscosity of the polymer, but for an intrinsic viscosity of 0.67, pack temperatures in the range 280-286 C. are suitable. The lower limit of intrinsic viscosity for satisfactory spinning is 0.39. Below this figure the frequency of threadline breakdowns becomes too great for the process to produce good quality spun tow.

Preferably the quench surface is of such a size and shape and in such a position that freely falling filaments do not foul the unit. To achieve this the largest horizontal diameter of the quenching body to be used inside a conical array of spinning filaments, must be less than the diameter of the circular row of spinneret holes by at least In the preferred design, this measurement is /3. It is important that the quenching surface shall be so shaped as to provide a gentle lead-in for the spinning filaments. In the preferred design, the upper portion of the quenching body, is acting as a lead-in for the filaments, and may be conical or convex. A tangent to this upper portion is preferably inclined at 20 to a corresponding tangent on the main quenching surface, which may be conical or convex, An undesirably abrupt change of slope at the junction of the two conical or convex surfaces is avoided by blending the two surfaces together by a third gently curved surface whose radius of curvature in the vertical plane containing the axis of symmetry of the quenching body is not less than A". A greater lead-in angle could safely be used if the radius of curvature of the blending surface between the upper and lWc1 part of the cone were also increased.

The as-spun filaments may be combined into a tow e.g. of 600,000 denier and drawn in steam to 2.0 to 4.0 times their original length. If desired, a Water drawing process can be used and in this case a draw ratio of 23.5 must be followed by a second draw of l20% applied in a separate stage whilst the tow is heated e.g. by a hot plate, to at least 110 C. If this extension stage is omitted then the final crimp is very poor. The drawn tow is highly crimped and very bulky when the tension is relaxed. The tow is then cut and the fibres are heat set. This unusual step of heat setting after cutting is essential to our process because it allows rotation of the crimped fibres about their axes, an action which enhances the crimp. Suitable temperatures for heat setting are 130- 200 C. In a particular case the Crimp index and crimp level (crimps per straight inch) of fibres when heat set before cutting were 26% and 2.7 respectively Whereas when cutting preceded heat setting the corresponding crimp figures were 42% and 3.1. A preferred range of crimp index is 3550% and a crimp level of 2.5-3.5.

It is important that the fibres are well separated from one another and not grouped together in bundles before the heat setting process, as may happen as a result of surface tension of water or other fluid on the fibres. If fibres are restricted, during the setting process the crimp in the final product will be drastically reduced. Thus the manner and timing of the application of aqueous finish are important. If finish is applied to the tow immediately before cutting, it must be applied with the minimum of moisture, consistent with getting a sensibly uniform distribution of agent upon the fibres. When steam drawing is employed, finish may be applied from a bath prior to the drawframe but the wet drawn tow must be mangled to reduce the liquid content of the tow to at most 30% by weight before the tow is out. In addition it is desirable, to include a stage of drying before cutting providing that the tow temperature in this stage does not exceed 60 C. When water bath drawing is employed, the finish may be in solution in the draw bath itself and the subsequent heating of the tow under tension has a valuable drying effect also. However if finish cannot be applied in the draw-bath it will be necessary to apply at least an antistatic agent to the hot dry tow after drawing. In the absence of such a precaution the tow is troublesome to handle.

Crimp index is defined as where l and 1 are respectively the fibre lengths measured under loads of 0.1 g./den. and 0.005 g./den. respectively. Crimp level is the number of helical turns including fractions, in length 1 divided by length 1 The mean rate of change of instantaneous modulus between 5% and extension is obtained from a curve of specific load in gram/ denier and extension, by taking the difference between the tangent slopes at the 5% and 10% points measured in gram/denier/unit strain and dividing by 0.05.

The accompanying drawing, which is a diagrammatic sectional side view of a spinneret with quenching body, shows a part of an a paratus suitable for making the fibres of our invention.

Referring to the drawing, filaments coming from a circular spinneret 1 with a row of holes 2 in an annular trough 3 and arranged in a circle are taken to a ceramic traverse guide (not shown) associated with a windup mechanism. Between this and the spinneret 1 there is a quenching body 4 consisting of a hollow porous ceramic shell 6 with an inlet 5 for the quenching liquid. The largest diameter of the quenching body 4 which is of circular shape in plan View, is 3.5 tapering at the lower end to 3.25". The top tapers to a smaller circular diameter and forms the upper part of the quenching surface. Tangents between the upper and lower portion of the quenching surface which may be convex, but which is drawn as a two cone, is 20 of angle. The top and bottom of the ceramic shell is sealed by rubber gaskets 8, which are held by brass plates 9 and 10 by means of clamping screws 11 and 12 which may be tightened on thread 13.

The distance between the spinneret orifice and the first contact point on the quenching surface is 5".

A convergence guide in the form of a circular ring is 5 feet below the quenching surface lower down along the threadline.

The following examples illustrate but do not limit our,

invention.

EXAMPLE 1 Polyethylene terephthalate of intrinsic viscosity 0.67 if melt-extruded through a spinneret with 154 holes each of 0.015 inch diameter arranged in a single circle of 2.093 inches radius. The temperature of the wall of a filter sand pack immediately adjacent to the spinneret is maintained at 283 C. The spun filaments are wound up on a bobbin at a linear speed of 3,000 ft./ min. The denier of the spun tow is 1670. A hollow conical porous ceramic quenching body whose maximum diameter is 3.313 inches and whose depth is 1 /2 inches is interposed between the spinneret and wind up unit so that the bottom of the quenching body is 6 /2 inches below the spinneret. Water at room temperature is flowing from the inside of the quenching body to the outer surface at 135 cc./min. and the melt spun filaments are held in contact with the conical ceramic surface by the surface tension of the water. The spun tow is creeled to give a total denier of 50,000 and drawn to a ratio of 1:3.3 in a steam bath. The drawn tow is then mangled, heated at a temperature of 55 C. for 3 minutes whilst under no tension, sprayed with an aqueous solution of a textile finishing agent, cut to 1 /2 inches and heat set for 12 minutes at a temperature of 135 C. in an air oven. These fibres have a tenacity of 4.3 gram/denier, an extension to break of 51.5%, an initial modulus of 32.8 gram/denier, a crimp index of 35%, a crimp level of 9 crimps per straight inch, a denier of 4.2 and a mean rate of change of instantaneous modulus in the range 510% extension, which lies within the range of -160 gram/ denier. The fibres also show a difference of refractive index between the two sides of the fibre greater than 2.10 The fibre was made into batts weighing approximately 1 lb. per square yard. After repeated uniaxial loadings to a pressure of 10 gm./cm. the specific volume of the batt was found to be 36 cm. /gm. under this pressure.

EXAMPLE 2 Polyethylene terephthalate of intrinsic viscosity 0.67 is melt-extruded from a spinneret having 154 holes, each 0.015 inch in diameter disposed in a circular arc of radius 2.093 inches. The spun tow denier is 1850 and the wind up speed is 2,500 ft./min. A conical porous ceramic quenching body is placed symmetrically inside the array of spinning filaments. Water is percolating to the outside surface of the quenching body at the rate of cc./min. The temperature of the wall of the sand pack adjacent to the spinneret is 282 C. The spun tow is creeled to give a denier of 100,000 and then drawn in steam to a ratio of. 1:3.3, mangled, sprayed with a finishing agent, cut to 4 inches and then heat set for 4 minutes at C. The fibres have a crimp index of 25%, a crimp level of 8 crimps per straight inch, a tenacity of 4 gram/denier, an extension to break of 50%, an initial modulus of 29 gram/denier, a mean rate of change of instantaneous modulus between 5 and extension within the range 90-160 gram/denier and a denier of 4.3. The difference of refractive index between the two sides of the filament is 2 10' These fibres are processed to 1/28 worsted count yarn with 9 turns per inch Z twist after which two ends of the yarn are plied with 6 turns per inch S twist. The yarns are woven in a plain weave fabric which is blown, scoured, dried, cropped and heat set. Fibres which have been mechanically crimped and which are of the same length and denier as the helically crimped fibres are processed to the same yarn count and'twist, the yarns being subsequently woven into a plain weave fabric which is finished as described above. Both the wet and the dry crease recovery is measured for both helically crimped and mechanically crimped samples using the Shirley combined creasing and stiffness tested. The fabric thickness i also measured in each case under a load of 0.7 psi. and the fabric specific volume calculated. The table illustrates the superiority of the helical crimped sample over the mechanically crimped sample.

What is claimed is:

1. A process for making crimped filaments from a synthetic linear polyester, the process comprising melt spinning the said polyester from a plurality of orifices such that the hot filaments, during their travel to a winding device, are cooled asymmetrically by contacting them with a continuously renewed thin film of a liquid on the surface of a solid body where the temperatureof the liquid is substantially below that of the melting point of the polyester, where the film of liquid is thin enough to contact one side only of each filament, but sufficient to hold the filaments in contact with said solid body where the length of contact of each filament with the liquid film is at least /2 inch and where the point of first contact of each filament and the liquid film is between 4 and 14 inches below the extrusion orifices, drawing the filaments at a draw ratio of 2 to 4 times, releasing the tension on the drawn filaments to allow the spontaneous development of crimp, cutting said drawn filaments and heating the filaments substantially free of tension at a temperature in the range 130 C. to 200 C.

2. A process as in claim 1 wherein said solid body on which the liquid film is present being conical and tapering in the direction of filament movement, and wherein said filaments are spun in an annular pattern and are held inwardly toward the axis of the pattern so as to contact the tapered surface of the solid body.

3. A process according to claim 1 in which the tension of the filaments passing over the quenching surface is between 0.02 gm./den. and 0.06 gm./den.

4. A proces according to claim 1 in which the filaments are wound up at speeds of about 3,000 to 4,000 feet per minute.

5. A process according to claim 1 in which the flow rates of the qupenching surface employed are 0.5 to 1.5 cu. cm./minute per sq. cm. of useful quenching surface.

6. A process according to claim 5 in which the flow rates on the quenching surface to the filament number is 0.5 to 0.9 cu. cm./minute per filament.

7. A proces according to claim 1 in which the polyester is polyethylene terephthalate having an intrinsic viscosity between 0.39 and 0.67 using meltspinning pack temperatures in the range of 280 to 286 C.

8. A process according to claim 1 in which filaments are combined into a tow and drawn in steam to 2 to 4 times their length as spun.

9. A process according to claim 1 in which the meltspun filaments are subjected to a water drawing process at a draw ratio of 23.5 :1, followed by a second draw of l-- 1.2:1 in a separate stage while the tow of filaments is heated above 110 C.

10. A process according to claim 1 in which the fibers are well separated from one another and not crimped together in bundles before the heat setting process.

11. A process according to claim 1 in which the wet drawn filaments are mangled to reduce the liquid content to at most 30% before cutting.

12. A process according to claim 1 in which the filaments are dried before cutting using temperatures which do not exceed C.

References Cited UNITED STATES PATENTS 2,324,397 7/1943 Hull 264176 3,008,186 11/1961 Voigt 1814 3,120,027 2/1964 Baggett et al l8-8 3,385,918 5/1968 Jack et al 264'89 FOREIGN PATENTS 454,655 1949 Italy 264-176 F 550,013 1956 Italy 264-l76 F 809,273 2/1959 Great Britain 264176 F 366,119 1/1963 Switzerland 264176 F JAY H. WOO, Primary Examiner US. Cl. XJR.

28-72 HR; 264-l76 F, 210 F, 290 

